1. Field of the Invention
The present invention relates to a transparent conductive film capable of showing excellent display quality when used for a display or the like and good handling properties in the course of manufacturing, processing or the like. The present invention also relates to a touch panel and an electroluminescent display panel that use such a transparent conductive film. Furthermore, the present invention relates to a process of producing the transparent conductive film.
2. Description of Related Art
Transparent conductive films function as electrodes, and, in addition, have transparency, so that it is possible to see objects through these films. They are, therefore, often used as electrode sheets for display panels of various modes or touch panels to be placed on the surfaces of displays.
For example, such a transparent conductive film is obtained by laminating a transparent conductive layer of ITO (indium tin oxide), ATO (antimony-doped indium tin oxide) or the like to the surface of a transparent plastic film such as a polyethylene terephthalate resin film.
In the case where the above-described transparent conductive film is used for a display panel or touch panel, it has sometimes been subjected to anti-glaring treatment, in which a mat paint is applied to the transparent conductive film for the purpose of decreasing reflection of extraneous light. If a mat paint is applied to the transparent conductive film, the effect of preventing glaring can be obtained, but the following problems newly occur: an image on the display visible through the transparent conductive film appears fuzzy; the moiré pattern appears at boundaries between pixels on the display; and the central part of the display is strikingly seen due to its brightness higher than that of the other part.
Attaching great importance to transparency, on the other hand, there has also been adopted, to improve display visibility, such a means that the surface of the transparent conductive film is smoothed to a mirror surface to eliminate the scattering of light. However, a transparent conductive film having a mirror surface is extremely poor in surface slipperiness. Therefore, when such a transparent conductive film is processed by a roll-to-roll method (a method comprising: unwinding a continuous substrate such as a transparent plastic film; forming a transparent conductive layer on the substrate under vacuum by deposition, sputtering or the like; and winding, around a roll, the transparent conductive film obtained), such a phenomenon (blocking) tends to occur that one surface of the substrate sticks to the other surface of the substrate or that the substrate cannot smoothly run in the production unit. If blocking occurs, the transparent conductive film obtained cannot be rolled into a good shape, and the unrolled transparent conductive film has traces of blocking on its surface.
To prevent occurrence of blocking, it seems effective to employ such a technique that a blocking-preventing tape is adhered to or irregularities called knurls are provided on both sides of the transparent plastic film. To employ this technique, however, it is necessary to modify those sections of the production unit that correspond to a series of the steps of forming a transparent conductive layer by vacuum deposition or sputtering on an unwound substrate film, and winding the transparent conductive film obtained. In addition, after these steps, it is necessary to remove the tape adhered to both sides of the substrate film, or to remove both sides of the substrate film, on which the irregularities are provided, by a slitter or the like.